1. Field of the Invention
The present invention relates to a nozzle system of an injector, and in various aspects, to a nozzle system of an injector for a vehicle in which a structure thereof is improved and atomization performance of liquid that is injected is enhanced.
2. Description of Related Art
Generally, vehicles are classified as gasoline vehicles, diesel vehicles, and LPG vehicles according to types of fuel. The diesel vehicles among them have high power for high load as well as lower fuel consumption and thus have increasing demand.
However, more polluting materials such as nitrogen oxide and particulate material are included in the exhaust gas of diesel vehicles compared to the gasoline vehicles. Accordingly, a variety of exhaust gas filter apparatuses are under development so as to purify the diesel exhaust gas by processing the polluting materials.
One conventional solution is a selective catalyst reduction (SCR) apparatus which uses a catalyst so as to reduce nitrogen oxide that is included in the exhaust gas to nitrogen and oxygen. The application range for such a system is becoming broader. Research into a urea-SCR apparatus utilizing urea as a reduction agent has been actively conducted. The basic principle of such urea-SCR apparatus is to transform the nitrogen compound NOX, which is harmful to the human body, to harmless nitrogen N2 by a chemical reaction of ammonia and a catalyst.
FIG. 1 is a schematic diagram of a conventional urea-SCR apparatus. Exhaust gas is exhausted from an exhaust manifold of an engine through an exhaust pipe 10. As shown in FIG. 1, the SCR apparatus 20 is disposed in the exhaust pipe 10 in the flow of exhaust gas.
An injector 50 is disposed inside the exhaust pipe 10, wherein the injector 50 injects urea upstream of the SCR apparatus 20 according to flow of the exhaust gas. The urea is injected into the exhaust pipe 10 through the injector 50 in the form of aquatic solution. The injector 50 receives the urea from a urea tank 30, where the urea is stored, through a urea supply pump 40. The injector injects the urea into the exhaust pipe 10.
The injected urea is transformed to ammonia in the exhaust pipe 10 in which the urea is vaporized and decomposed by thermal energy of the exhaust gas. Further, nitrogen oxide that reacts with the ammonia is transformed to harmless nitrogen.
Accordingly, the operation to purify the nitrogen oxide is substantially performed not by the urea but by the ammonia. Accordingly, it is beneficial that the injected urea solution have excellent vaporization and thermal decomposition performance.
The vaporization and thermal decomposition performance of the urea can be improved as the particle size of the injected urea becomes smaller. Accordingly, there is a desire to improve the performance of the SCR apparatus by increasing the atomization performance of the urea.
One such solution focuses on the injector nozzle. The nozzle shape of the injector 50 can be variously changed so as to efficiently atomize the urea that is injected into the exhaust pipe 10. However, it is generally difficult to atomize the urea that is injected in a solution state.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.